Plasticization of plastics



Reiesued Dec. 3, 1946 PLASTICIZA'I'ION F PLASTICS John D..I

scum.

The preunt invention relates to the preparation and use of plasticcompositions and notably to those containing compatible plasticizers.

One object of the invention is to provide a simple and economicalprocess of uniformly dispersing compatible plasticizers with plasticmaterials in which they are employed as modifiers.

A second object of the invention is to provide a fluid compositioncomprising a high concentration oi plastic material, and a plasticizertherefor suitable for spraying, brushing or like applications. withoutrecourse to expensive solvents for the plastic.

These and other objects or the invention will be apparent iromconsideration of the following specification and the appended claims.

Plastics such as vinyl resins.'cellulosic plastics and the like arecustomarily compounded with modiiiers termed plasticizers. which enhanceplasticity, toughness, flexibility and homogeneity. If the plastic is tobe molded, sheeted. extruded. or otherwise shaped, the plasticizer maybe incorporated by milling. which is a relatively laborious operation.

In the preparation of coating compositions suitable ior spraying,brushing, dipping, or for application by other methods well understoodby the art. it is customary to dissolve the resin plastic and suchplasticizers as are required therefor in a suitable solvent in suchproportions as to obtain a requisite fluidity of the composition. Uponapplication of the composition to the bodies to be coated, the solventssoon evaporate leaving the plastic. plasticizer and other modifiers ascontinuous adherent films. One objectionable feature of such process isthat many of the desirable plastlcs are soluble only in certainrelatively active solvents which can only be obtained at substantialexpense.

Furthermore, plastics. in dissolving in solvents, tend to producesolutions oi high viscosity and unless the concentration is kept low.the solutions may be so viscous as to make it diiiicult to applythemasfilmstobodiestobe coated. Low concentration of plastic in thesolvent necessitates use of excessive amounts of solvent and applicationof an undesirably large number of coats to obtain desired filmthickness.

It has also been proposed to disperse solutions of resins with water orother non-solvent for the resins, to provide emulsions that can besuitably applied to a surface to be coated. The suspending medium andthe solvent for the plastic evaporate from a him of such material andthe particles of resin solution coalesce to form a solid. continuousfilm. Either process requires the use of solvents for the plastic.

In accordance with one feature oi the present invention it is proposedto disperse a plastic ma terial in finely-divided or powder form in aninenkim, Milwaukee, Wis. assign to Pittsburgh Plate Glass Company, Al orcounty, Pa, a corporation of DIIIIIIIINNO. 2,385,920. datedOctolegllelly Pennsylvania 024, December iii,

expensive medium which is a non-solvent there- 'for, and which containsin solution a plasticizer for the plastic, to provide concentratedsuspensions that can be sprayed or brushed or otherwise applied to abody to be coated in much the same manner as ordinary coating materials,without recourse to solvents.

Any suitable finely-divided plastic material may be employed inpracticing the invention. They include any of the usual synthetic ornatural resins or plastics commonly used for molding or for formingcoatings, which by themselves at ordinary temperatures may be obtainedas non-tacky powders. Plastics considered to be especially suitable forthe purpose included Vinylite X, a form of resin particularly designedfor use in safety glass and considered to embody a polymerizationproduct of polyvinyl alcohol and an aldehyde such as butyraldehyde.which polymerization is carried sufllciently iar to obtain a productwhich is substantially insoluble in water, but is not conducted to thestage in which the resin loses its solubility in all solvents.

Another form oi resin suitable for many purposes comprises the productsold under the trade name oi "Vinylite 1-1." This product is understoodto comprise a copolymer of approximately 87% of vinyl chloride and 18%of vinyl acetate. If desired. the copolymer may be replaced by a simplepolymer of either or its components. namely, of vinyl chloride or vinylacetate.

Vinyl resins may be replaced by cellulosic plastics including celluloseacetate. cellulose ethers of the type of ethyl cellulose, celluloseaceto-propionate and cellulose acetobutyrate. Phenol resins, namely thepolymerized products oi' phenol and formaldehyde, especially straight orunmodified phenolic resins in the intermediate or B stage of plymerization may be employed. Similarly, soluble urea resins obtained bycondensing urea or thiourea and mixtures of urea and thiourea withformaldehydes. such as formaldehyde are contemplated. These resins maybe modified by additions of certain amounts of alkyd resins obtained bycondensing and polymerizing phthalic anhydride or other dicarboxylicacid with a polyhydroxy alcohol. such as glycerol. These alkyd resinsmay themselves include such modifiers as fatty acids. e. g, oleic acid,stearic acid. or glycerides. such as drying oils from linseed or thelike source. The alkyd resins in general are relatively soft and solubleand constitute plasticizers for the other resins. Any otherthermoplastic resin or plastic. that may be obtained in finely-divided.non-agglomerating solid form, may be employed.

The preparation of powders of the resins suitable for use in thepractice of the invention may be efiected by various methods. The mostobvious method of course includes grinding or mechanicaiattrition.However. the material employed in the practice 01' the invention isreduced to a particle size or 200 mesh or less. The above method is notalways satisfactory for producin such finely-divided materials, notablywhere the materials are relatively tough and rubbery plastics of thetype of vinyl resins. Accordingly, it may be desirable in many instancesto resort to precipitation of the plastic materialirom a solvent inorder economically to obtain a pulverulent body suitable tor dispersion,in accordance with the provisions of the present invention. One suchprocess is disclosed in British Patent 498,396. This method involvesprojecting the resin while in solution as a very fine spray andprecipitating the resin while the solution is still finely divided.Another method especially applicable to polyvinyl acetals is disclosedin British Patent 481,532, and involves dissolving the resin in a waterimmiscible solvent, such as chloroform or methylene chloride. Thissolution is then emulsified at high speed in water and in the presenceof a dispersing agent such as sodium butyl naphthalene sulionate. Thesolvent is removed by steam distillation. A further method is disclosedin German Patent 670,212 and involves dissolving the resin in a liquidunder pressure, which liquid is gaseous at ordinary temperatures. Sulfurdioxide and methyl chloride are suggested for the purpose.

A preierred method for purposes or the present invention involvesdissolving the plastic material, e. g., a polyvinyl acetal or acopolymer oi vinyl acetate and vinyl chloride. vinyl acetate, methylmethacrylate, or the like in a solvent, adding a non-solvent to thesolution approximately to the point of incipient precipitation oi theplastic, and then cooling and agitating the solution in order to eflectgelling, and subsequent separation of the plastic as a finely-dividedsolid which can be removed from the solvent by washing or other methods.to increase the concentration or nonsolvent.

Examples of the method are as follows:

Example A About 150 parts or the resin obtained by partial condensationoi polyvinyl alcohol with butyraldehyde was dissolved in 050 parts ofsynthetic methanol. To this solution under agitation at room temperaturewas added 90 parts of water. The resin was partially precipitated duringthis addition but redissolved upon continued agitation to a clear fluidsolution. The charge was continuously agitated and was gradually cooled.At 18' C. the charge became translucent and started gelling and at 5 C.the gel was quite heavy and viscous. Very strong agitation was requiredto keep the solution homogeneous at this point. At -8 0. some syneresisoccurred and at 10 C. the gel began breaking and precipitation started.At C. the resin had precipitated and the product was in fluidsuspension. It was further cooled to C. and an additional 2000 parts orwater was added at this point to harden theresin. The mixture was pouredinto 3000 parts oi water at room temperature and the product wasisolated by nitration. It was dried in a current of air at 25 C. toyield a very light flufly powder, 94.7% of which readily passed a 200mesh sieve. Under the microscope the particle size appeared to be veryunii'orm and in the'neiehborhood of 1000 mesh.

Theiilteredresinmaybedriedetenytemperature below its softening pointwithout serious coalescence or the resultant powder. A tempera- 4 tureof 45-50 C. has been found generally most satisfactory for polyvinylacetal resins.

Example B A solution was prepared by dissolving under agitation at roomtemperature, 100 parts of the resin obtained by copolymerizing, 8'!parts or vinyl chloride and 13 parts of vinyl acetate in 900 parts ofacetone. To this solution under agitation were added 320 parts oi 88%isopropanol. Particles oi resin precipitated during this addition butredissolved readily upon continued agitation. There resulted a slightlyhazy but very fluid solution which was gradually cooled. At 5 C. thesolution had become very hazy and quite viscous. At -4' C. the resinprecipitated in very finely divided form to yield a fluid suspension.Cooling to i0 C. brought no further change in the appearance oi thesuspension.

An additional 700 parts oi 88% isopropanol were added at -40 C. andimmediately thereafter 1500 parts 01 water raising the temperature to 24C. The charge was then dropped into 1000 parts of water at roomtemperature. After filtering and drying, less than 2% of the powderfailed to pass a 200 mesh sieve.

Example C Fii'ty parts of a commercial polymerized methacrylic resinknown as "Acryloid -27" were dissolved in 450 parts or acetone. To thissolutim under agitation at room temperature were added 75 parts oiwater. The resulting clear bolution was gradually cooled. At 9 C. it wasviscous and haziness appeared. At 2 C. it was very hazy and viscous andrequired strong agitation to keep the mixture homogeneous. Between 0.and -5 C. the viscosity decreased very rapidly indicating that the gelhad broken and the resin precipitat-ed. At -8 C. an additional 500 parts01 water were added alter which the charge was dropped into 6000 partsof water at room temperature.

Ai'ter mixing 1 hour the resin was filtered and was subsequently dried.It was then obtained as a fine powder the major portion of which readilypassed a 200 mesh sieve.

Example D A sample of polyvinyl alcohol was prepared by the hydrolysisof low viscosity polyvinyl acetate by the method described by Blaikieand Crozier, J. Ind. and Eng. Chem. 28 1158 (1936). According to thismethod 50 parts 'of the polyvinyl acetate known commercially as VinyliteAYAA" were dissolved in 100 parts at synthetic methanol. A solution of0.25 part 01 caustic potash in 10 parts or. methanol was added. Afterseveral hours, the solution had set to a gel and after 10 hours, arubbery gel remained covered by a clear mixture 0! methyl acetate andmethanol. The solvent was decanted and the gel was dissolved in water.The resulting solution was held at 90-100 C. until the residual methanoland methyl acetate had been distilled. Additional water was then addedso that the dual concentration corresponded to the addition of 330 partsoi water.

To this solution under agitation was added 330 parts 0! acetone byvolume. It was then chilled gradually to 10 C. where it gelled. At 20',the gel started synerizing and at -25' the gel was definitely broken andthe product had precipitated. At 25 to 30 C. 1000 parts of acetone wereadded and the resulting suspension wasallowedtowarmtoroomtemperatureandwas filtered. The filter cake waswashed with 1000 parts of i'resh acetone and was then dried in an ovenat 65 C.

The product was thus obtained in dry lumps which were readily crushedunder light pressure to a ilne powder. All but '1 oi the product readilypassed a 200 mesh sieve.

Example E Forty parts of a commercial resin obtained by polymerizingethyl methacrylate were dissolved in a mixture consisting of 316 partsof 99.5% alcohol and 60 parts of acetone by volume. The solution wasagitated at room temperature and there was added a. solution consistingof 40 parts of water in 100 parts of alcohol. The solution becameslightly cloudy but no precipitation occurred. It was then graduallycooled. At 15 C., the solution had become quite cloudy and 12 C. itbegan to gel. At C. the gel started to break and at 5 C. the gel hadbroken and there was a very fluid suspension. The charge was cooled to-15 C. and was there diluted with 140 parts of water. It was then pouredwith 2500 parts or water to form a fine suspension.

The suspension was filtered and the cake was washed with water. It wasthen dried in an oven at 50 C. to form soft lumps which broke readilyinto a flufly powder. Essentially all of the powder passed a. 200 meshsieve.

For purposes of forming suspensions of the plastic which suspensionsembody a plasticizer for the final films or other bodies, thefinelydivlded plastic is incorporated with a liquid medium which isessentially non-solvent for the plastic, but which is a solvent for theplasticizer to be incorporated with the plastic. It will be apparentthat if the precipitation method above described is employed to disperseor break up the plastic, the original precipitation or drowning mediummay be employed as a medium for eil'ecting the incorporation oi theplasticizer. Thus in Example 13, as above given, the plasticizer may beadded to the resin suspended in finely-divided form in isopropanol.

A preferred method in many instances, however, involves removal or theprecipitant by filtration, or filtration and evaporation and subsequentaddition of an inexpensive organic nonsolvent such as mineral spirits,petroleum ether or the like, which can be obtained at an expense of buta few cents a. gallon. The plasticizer can then be added and soondissolves in the nonsolvent for the plastic.

Simultaneously any plasticizers, which are reasonably soluble in thenon-solvent dispersing medium for the specific plastic contemplated, maybe employed. A few suitable combinations of non-solvents andplasticizers for certain plastics are tabulated as follows:

NITROCELLU LOSE Non-solvent Plasticizers M inoral spirits Glycol otherplasticizers Toluene 'lricresyl phosphate Carbon tetrachloride, etc.Castor oil CELLULOSE ACETATE Mineral spirits Carbon IetrachlorilleTurpeni inc, etc.

Dimethyl phthalnte Phtlialic acid ester of monomoihyl ether oi ethyleneglycol, etc.

CELLULOSE AOETO-PRDPIONATE or BUTYRATE Petroleum naphtha Dlbutylphthalatc UREA-FORM ALDEHYD E M inoral spirits Petroleum naphthaTurpentine, ctc.

Soft alkyd resins VINYL ACETATE POLYMER M incrnl spirits Turpentine,etc.

Dihntyl phthalate 'irlcresyl phosphate VINY L CHLORIDE .Nlincral spirits'lurpenline, vic.

Dibutyl phthalate Tricresyl phosphate PARTIAL POLY-VINYL ACETAL 0RBUTYRAL Petroleum na htha Dibutyl phthalete l i yrirogenate naphtha(etano Triethylenc glycol dlhexoate COPOLYMER 87% VINYL CHLORIDE 13%VINYL ACETATE 'letrahydro naphthalene Dipentcne, petroleum spirits,

hntyl alcohol Propyl alcohol Dlhutyl phthalate Tricresyl phosphate C11LORINATED RUBBER Petroleum naphtha Chlorinated diphenyi 'lricrcsylphosphate M E'IHYL ME'IHACRYLATE RESIN Dibutyl phthalate M incralspirits SH ELLAC M incral spirits Dibutyl phthalato MANILA GUM Mineralspirits Dibutyl phthalate STYRENE RESIN M incral splriis Dibutylphthalate CO UMARONE-INDENE Butanol Linseed all For most purposes, arange of non-solvents of about 30 to 90% with a preferred range or about50 or 60% upon the basis or the complete formula is satisfactory. thoughfor special purposes lower and higher proportions may be employed.

same

The plasticizers may be added in any amount less than that at which theresin tends strongly to gel in the non-solvent. For most purposes about25 to 100%, based on plastic content is satisfactory.

Pigments such as carbon black, titanium dioxide, white lead and othersmay be added in appropriate amounts (2 to 300% more or less) based onplastic content of the formula. The pigments may be dispersed in thesuspension or may be dispersed in the plastic or resin solutions priorto comminution of the resin.

It will be evident that mixtures, in practically any proportion, e. 5.equal parts by weight oi any two or more oi the plastics hereindisclosed. may be plastlclzed simultaneously, or two or more compatiblepulverized and plasticized plastics may be admixed. Drying orsemi-drying oils (scya bean, etc.) and resins may be added. Similarlycompatible plasticizers may be admixed.

For example, suspensions of "Vinylite H, i. e. copolymer of vinylchloride and vinyl acetate, may be modified with appropriate amounts (10to 50%, more or less) or normal butyl methacrylate resin, Bakelitemodified with ester gum, or simply with ester gum. Nitrocellulose may bemodified with glycerol phthalates, ethyl cellulose, vinyl acetate, gumdamar or ester gum modified phenolic resin. Ethyl cellulose may bemodified with methyl acrylate resin, cellulose acetate, phenolic resin,coumar, damar, rosin, alkyd resins, etc.

The modifiers may be added to the base Plastic at any time, e. g. beioresolution preparatory to precipitation of the powder, or to the solution,prior to precipitation. In some cases suspensions of the two plastlcsmaybe admixed or in event that the added resin is soluble in thenon-solvent tor the base resin, a suspension oi the base resin in asolution of the added resin may be formed.

Alkyds, notably the soft, modified alkyds, may be dissolved insuspensions of vinyl acetals or vinyl acetate-vinyl chloride copolymers,in mineral spirits or other non-solvents. When the liquid evaporates thedissolved resin sets either as a binder about the particles of solidresin or forms a compatible mixture therewith, It is, or course,desirable that the proportion of dissolved resin be not so great as toinduce gelation of the suspension. In most cases, 5 or based on totalresin content or more can be added safely.

Solvents in limited amounts may be added to suspensions of plastics innon-solvents. A par- .ticularl interesting system involves a combinationof a relatively volatile non-solvent and a solvent oi lower volatility.As the non-solvent evaporates, the concentration of solvent increases tosuch extent that the plastic becomes so softened as to induce cohesionof the particles into a, homogeneous mass. Subsequent fusion of films ofsuch material by heat may not be required.

A typical system of this type would comprise a suspension ofnitrocellulose plasticized with dibutyl phthalate and suspended in hightest gasolene to which was added amyl acetate as a solvent ior thenitrocellulose. A typical formula of this type might be approximately asfollows:

Example I Per cent Nitrocellulose (powder) 20 Dibutyl phthaiate 10Suspension medium 70 The suspension medium comprising:

Amyl acetate 10 Examples in which the low volatility solvent is omittedare:

Example 1'] Per cent Partial poly-vinyl butyral powder 14 Dlbutylphthalate 6 Titanium dioxide pigment 20 Petroleum spirits Example IIIPer cent Partial polyvinyl butyral powder 21 Dibutyl phthalate 9Petroleum spirits '70 Example IV Per cent Partial polyvinyl butyral oracetal powder 14 Dlbutyl phthalate 6 Carbon black 3 Petroleum spirits 77Example V Per cent Copolymer of vinyl chloride and acetate powder 20Dibutyl phthalate '1 Tricresyl phosphate 3 Normal butyl methacrylate l0Mineral spirits 60 Example VI Per cent Copolymer of vinyl acetate andvinyl chloride (powder) 20 Ethyl cellulose (powder) l0 Tricresylphosphate 'l Dibutyl phthalate 3 Mineral spirits 60 The composition wasapplied by spray to metal panel and baked for 20 minutes at C. toprovide a hard and strongly adherent film.

In any of the examples as well as in other applications of the inventiondispersing agents such as sulfonated castor oil or sodium salt ofdibutyl naphthalene sulfonate in small percentages may be added topromote and maintain dispersion of the plastic particles.

It will be apparent that films after drying may be simply sprayed with avolatile solvent to provide homogeneous films. Objects coated with thedispersed plastics may be passed through chambers filled with solventyapors or mists to produce softening. Thus films of the material inExamples I to V1, instead of being baked to induce plastic flow andcoalescence oi the particles, may be merely wet with acetone or othersolvent or exposed to vapors thereof, or subjected to heat and/orpressure as by a roll.

Suspensions of partial polyvinyl acetal resin the grade used in safetyglass in mineral spirits and about 30% of a compatible plasticizer suchas triglycol dihexoate may be spread upon glass plate and dried. Theplates may then be superposed without cements and subjected to atemperature of 100 C. or upward and to direct fluid pressures of 10 or15 atmospheres to cause them to adhere, thus providing safety glass ofhigh strength. v

Suspensions of plastics in solution of plasticizers in non-solvents forthe resin, for instance those of Example III, or any of the plasticscontemplated for suspension, may be spread upon the traveling surfacesof drums or bands of polished chromium or other stripp ng surfaces andbaked to provide films that may be removed by stripping and used as areinforcement ior'safety glass or for other purposes. Suspensions ofresins without plasticizers may also be employed to form films.

Suspensions of the plas ics may be added to paper pulp as a size or maybe spread upon sheets of paper to give a surface finish.

Example VII Percent Partial polyvinyl butyral resin (powder) i 21Dibutyl phthalate 9 Kerosene 70 The suspension was spread with a bladeupon a, sheet of paper. The sheet was baked at 100 C. to evaporate thekerosene and to provide an adherent, water-resistant, low gloss coatingexcellently adapting the paper for use as a wrapping for food products,such as cheese and the like.

Cloth, such as cotton or linen or rayon, may be coated or sized withvinyl chloride acetate copolymer, vinyl acetal or other resin in similarmanner, or fabrics may be dipped in a thin suspension and then wrung.Loosely woven fabrics such as are used as liners in collars or necktiesmay be permanently sized with a permanently thermoplastic resin of thetype of partial polyvinyl acetal as described in Example VII, or of thecopolymer of vinyl chloride and vinyl acetate as disclosed in Example V,to provide a product that will withstand repeated laundering and ironingand will bond the inner and outer layers together.

Suspensions. such as herein described, may be applied as coatings overfilms of regenerated cellulose, cellulose acetate, cellulose nitrate,casein. rubber hydrochloride and the like impermeable fims, and theparticles dried and coalesced by flash heating or by application ofsolvents or solvent vapors to increase resistance to moisture, solventvapors, or to provide surfaces that can be united by heat or solvents toprovide wrappers for food products or other merchandise. The suspensionsshould be made in non-solvents for the films to be coated.

In a further application of the invention, suspensions of plastics withor without fillers such as wood flour, paper pulp or the like innonsolvents as herein described may be applied to porous moulds ofappropriate contour. The liquid medium is absorbed in, or drained out ofthe mould to leave films of resin that follow the contour of the mould.The resin may be consolidated by heat. The mould may be removed, orretained as a reinforcement in the finished body.

10 Example VIII A mould may be formed of plaster of Paris or the likeand illed or partially filled with a paste or slurry of afinely-divided, thermoplastic resin su'eh as Vinyl 2:" (partialpolyvinyl butyral) in mineral spirits. A plasticizer such as dibutyl'phthalate in appropriate amount, e. g., 20 or 30%, based on resin,fillers such as wood pulp in amounts of for example 40 or 60, based ontotal solids may be added. The slurry in proper amount is poured intothe mould and let stand a few minutes. The excess is then poured off.The mould with the desired coating therein is left to stand for an houror longer and the article in it is then sprayed with ethyl alcohol.After it has stood a further period of several hours the moulded articleis removed and baked at 100 C. or thereabout to form a coherenthomogeneous mass.

In order to provide an improved flatted varnish, resins. such as aVinyi.ite X" or Vinylite H" or ethyl cellulose in suspension in anosolvent, as herein described, may be admixed with drying oils or otherpaint or varnish-forming material which is a non-solvent for thesuspended plastic in amounts of about i to 20%. based on the totalnon-volatile content. Films of oils or varnishes so treated are ofexcellent, non-glossy appearance. They possess excellent strength andadhesion. They may be baked without loss of the flatting effect and arein other respects highly satisfactory. The suspensions of resins asherein described, for instance in Examples I to V1, are highly suitablefor use as flatting agents in drying oils, either alone or whencompounded with pigments, modifiers, etc.

For purposes of preparing a printing ink, a very finely-dividedthermoplastic plastic, e. g., ethyl cellulose or the like, most of whichwill pass a screen of 200 to 1000 mesh, or even finer, is suspended,preferably along with a plasticizer, in a non-solvent for the plastic.Coloring matter, such as carbon black. dye, etc., may be incuded inamounts of and upward, based upon plastic content. Drying oils, such aslinseed, tung and the like may be included in amountsof 20% or more upona like basis. The formulations given in Examples IV and VI. to whichcarbon black or other coloring matter in appropriate amount has beenadded may be employed. These inks, with enough non-solvent to giveproper fluidity, are applied to paper, e. g., newspaper stockbyconventional presses. The porous paper immediately absorbs much of the55 dispersing liquid, leaving the particles oi plastic adhering to thepaper in the desired pattern.

The print is quickly passed over hot rolls or under radiant heaters torapidly evaporate the solvents and to fuse down the plastic intoadherent 60 homogeneous state upon the paper. The paper may then becooled by blasts of cold air or by passing it over cold rollers.

Drying of the film in printing is very rapid and at most requires but afew seconds. This is 65 of great advantage in high speed printingbecause it admits of high production with relatively small dryingapparatus. It also reduces blurring of print.

It is to be understood that webs of paper, cloth 70 or other material,after printing, coating or im pregnation, may be passed through chambersfilled with vapors of a volatile solvent designed temporarily to softenthe plastic the point at which particles will cohere to eacl ...her andad- 75 here to the Pap In some instances the use of a plasticizer forresin is not required. For example, it may not always be required in theproduction of plastic suspensions suitable for use as prin i inks. ascoatings for paper or cloth, or other surfaces; a suspension oifinely-divided resin such as vinylite "X" orljH" in a volatile,plasticizer free, nonsolvent for xthe resin may be applied to porousbodies or other surfaces and then freed oi soivents and the resinsintered down to coherent state, by application of heat.

What I claim is: I

1. A coating composition comprising a finely pulverulent thermoplasticorganic plastic, a. volatile liquid which is a non-solvent for theplastic in which the particles of the plastic are suspended and apermanent, compatible plasticizer for the plastic dissolved in saidliquid, said plastlcizer being present in substantial amount but lessthan an amount at which said plastic tends strongly to gel in saidliquid non-solvent.

2. A coating composition as defined in claim 1 in which the plastic is avinyl acetal.

3. A coating composition as defined in claim 1 in which the organicplastic i cellulosic.

4. A coating composition as defined in claim 1 in which the organicplastic is a polymer of a polymerizable vinylic compound.

5. \A method oi. coating 9. surface which com-- pr applying thereto afilm o! a coatingcomr .tion comprising a finely pulveruientthermoplastic organic plastic, a volatile liquid which is a non-solventtor the plastic in which the particles oi the plastic are suspended anda permanent, compatible plasticizer tor the plastic dissolved in saidliquid, said plasticizer being present in substantial amount but lessthan an amount at which said plastic tends strongly to gel in saidliquid non-solvent.

6- A method of coating is surface which comprises applying to thesurface a. film o! a suspension of finely divided thermoplastic organicplastic material in suspension in an organic liquid medium which is anon-solvent tor the plastic, said medium containing dissolved therein acompatible plasticizer for the plastic. the liquid medium being presentin an amount within the range of to per cent based on the completeformula and the plasticizer being present in an amount within the rangeof 25 to per cent based on the content 0! said organic plastic materialtherein.

'7. A method as defined in claim 6 in which the liquid medium is presentin an amount within the range or 60 to 60 per cent of the completeformula.

8. A method as defined in claim 6 in which the organic plastic materialis ceilulosic.

9. A method as defined in claim 6 in which the organic plastic materialis a vinyl compound.

JOHN D. JENKINS.

Disclaimer Re. No. 22,812.-Joim D. Jenkins, Milwaukee, Wis.PLABTICIZATION or PLASTICS. Patent dated Dec. 3, 1946. Disclaimer filedMar. 15, 1948, by the assignee, Pittsburgh Plate Glass Company.

Hereby disclaim all coatinglcompositions covered b claims 1 to 4inclusive of said patent except those in whic the combination of puverulent lastic and plasticizer, but for the presence of thenon-solvent, would result in the ge ling of the plastic particles to thepoint of coherence;

And disclaims all methods of coating covered by claim 5 except thoseinvolving the application of a film of a coating composition in whichthe combination of pulverulent p astic and plasticizer, but for thepresence of the non-solvent, would result in the gelling of the lasticparticles to the point of coherence;

And further disclaims all methods of coating covered by claims 6 to 9inclusive except those involving the application of a film 0 asuspension in which the combination of finely divided lastic andplasticizer, but for the presence of the non-solvent, would result inthe gelling of the plastic particles to the point of coherence.

[Oflicial Gazette April 13, 1948.]

